Piezoelectric optomechanics in a 3D microwave cavity: A route to microwave to optical transduction*

Numerous examples of microwave to optical transduction have been demonstrated for optomechanical systems. In most cases, the piezoelectric effect allows for microwave-mechanical coupling either through direct capacitive stimulation or by creating surface acoustic waves using interdigitated capacitors. Here, we inject a microwave signal into a 3D microwave cavity where a GaAs optomechanical crystal has been placed at the electric field maxima. This allows the microwave cavity to stimulate the GHz-frequency mechanical breathing mode in the optomechanical crystal through the piezoelectric effect, which is then read out using the telecom optical mode. The GaAs optomechanical crystal is a good candidate for low-noise microwave to optical transduction, as it has been previously cooled to the mechanical ground state n = 0.7 ± 0.4 phonons in a dilution refrigerator [1]. Moreover, the 3D microwave cavity architecture used in this experiment can be naturally extended to couple to superconducting qubits.

1. H. Ramp, et al., Phys. Rev. Lett. 123, 093603 (2019)